This invention relates to metal enclosed switchgear and more particularly to a vacuum circuit interrupter which is mounted on a movable truck insertable within the compartment of the switchgear equipment. Suitable interlocking means are provided for safeguarding operating personnel.
For the past years a significant growth in population of the urban areas of this country has taken place while at the same time the increased use of electrical power has compounded the problem of supplying the needs of this urban growth. Concurrent therewith, the public concern with esthetics has forced a re-evaluation of how to best serve the electrical loads of the future efficiently and at the same time satisfy the environmentalists. The basic answer in many cases has been to raise the traditional distribution voltages to a much higher level. The availability of high capacity metal-clad switchgear for 34.5 kV applications is providing a practical answer for an increasing number of utilities. This equipment must be available in compact, attractive lineups for both indoor and outdoor installations. The use of vacuum interrupters has enabled manufacturers to reduce equipment size by providing all of the well recognized advantages of metal-clad construction. In addition, high densities require that these new stations be built in already established urban neighborhoods. In some cases such substations are needed in the congested downtown districts or major cities. Here the requirements for pleasing appearance and compact size are even more extreme than in the recent past.
With the advent of full scale, high capacity substations at the higher voltage level, equipment flexibility becomes increasingly important. No longer can the concern of the manufacturer be concentrated on a simple high side transformer breaker. He must also be able to accomplish a variety of circuit configurations: the ring bus arrangement, the breaker-and-a-half scheme, as well as the more traditional double ended station with high capacity secondary main and tie breakers. Complex protective relay schemes are needed, and ways must be found to provide current transformers on both sides of the breakers to meet differential zone requirements. A variety of auxiliary equipment must also be accommodated: control power and potential transformers, arresters, and multicable terminations and bus duct connections.
The availability of vacuum switch interrupters has made it possible to utilize these devices to effect a reduction in the size of switchgear. The interruption efficiency and the compact size of the vacuum switch interrupter make it ideal for application where size is important. This has led to design of vacuum oriented metal-clad switchgear for use in distribution system applications at 34.5 kV.